Combined SIP Advanced and SIP Troubleshooting

Description

This is an advanced SIP and troubleshooting training that includes a lot of practical exercises. Functions such as transaction handling, dialogs, different error situations, timers and a lot of other topics are covered in detail. You will learn how SIP works within IP-telephony, as well as multimedia solutions, such as presence and Instant Messaging (IM). This course will cover how SIP works both in wireline and wireless solutions and you will need basic knowledge within VoIP and SIP to participate in this course.

After a discussion about classic troubleshooting methodology each chapter is interleaved with a troubleshooting exercise where the students should find errors, and come up with solutions with which to fix them.

Target group

The target group for this course is people that need to understand the SIP signalling protocol in detail. Among these people we will find testers, developers and implementers, or as any engineer needing the ability to thoroughly analyse or troubleshoot a SIP network

Prerequisites

Basic knowledge within data communication equivalent to our course Data Communications Fundamentals , basic knowledge within within the TCP/IP protocol suite equivalent to our course TCP/IP and basic knowledge about Voice over packet networks equivalent to our course SIP Fundamentals.

Knowledge Test
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Other

This course is available as scheduled training and the presentation is given in English. The course is mixing theory and practical exercises. We can also give this course as on-site training. If you are interested in customized education, don’t hesitate to contact us for further information.

Agenda

Day 1-3

VoIP Signalling Overview

Functional components of a Voice over IP Network
The need for VoIP signalling and the different alternatives
- SIP, H.323, MEGACO, BICC
- IETF Multimedia Architecture
- Signalling and User plane separation
Brief repetition of RTP and RTCP

SIP Refresher and SDP Update

Background, history and Internet heritage
Main components; servers and clients.
Benefits and rules with different transport protocols
- UDP, TCP, SCTP.
Basic sessions and SIP mobility features
- Proxy and Redirect mode
- SIP Methods & Response codes
- SIP Registration
Session Description Protocol
- SDP Offer/Answer Model
- Quality of Service Extensions
- Connection Oriented Transports in SDP
- Media groupings in SDP

Basic Calls

Basic SIP sessions with SIP proxy and Registrar
Using Wireshark for traffic monitoring
SIP Signalling and SDP Negotiation analysis
Methods; INVITE, BYE, REGISTER

Protocol Foundation

Message structure and format rules
- Mandatory headers and parameters.
Proxy and Client DNS Usage
- NAPTR record type
- SRV record type
- A record type
SIP message routing rules
- Route headers
- Record Routing
- Via header response routing
Detailed proxy behaviour
- Location server lookup
- Request forwarding
- Response processing
Statefullness in SIP Servers
- Limitations of stateless servers
- Transaction and dialog-stateful servers
- Registration stateful servers
Creating early dialogs for early media

Call Signalling Details

Inter-domain call setup and routing
DNS usage
RTP details
SIP Header analysis
Usage of Request-URI
Record-routing examples
ReINVITE’s or UPDATE for session re-negotiation

Step by step walkthrough of advanced call scenario Features and Functionality

Extending the SIP protocol
- Using OPTIONS
- Negotiation extensions
- Requiring extensions
- Handling new SIP methods in old proxies
Reliable provisional responses
- PRACK
- RSeq and RAck
Forking and Cancelling requests
- Cancel and stateful proxies
Caller preferences and Callee Capabilities
- Addressing and Registration extensions
Using Early Media
- Simplex or Full-duplex
- Issues with forking.
Quality of Service and SIP
- Require Qos with SDP parameters
- Using UPDATE in early dialogs

Forking and CANCEL

Forking Calls When and Why?
Response processing at forking
Method: CANCEL
Parallell and sequential forking

Security

Firewalling SIP servers and clients.
Encryption and Authentication – How?
The Firewall and NAT problem
- SIP-away firewalls
- SIP signalling and NAT
- Symmetric Responses
- Managing Client Initiated Connections in SIP
- Media NAT traversal: STUN, TURN, ICE
SIP Privacy and Authenticity
- S/MIME examples for end to end security
- Privacy services
Securing the media channel

Security and DNS

User authentication and http digest
SIP symmetric responses
Understanding DNS queries

Services and Applications

Service creation possibilities with SIP
- Overview of SIP-CGI, CPL, Java servlets, Jain, Parlay
- Service examples with CPL
SIP Basic call-services and PBX-like features
- Call-forwarding, voicemail, CLIR/CLIP, etc
Call-transfer and Call-Pickup
- REFER and Replaces:
3rd party call control
SIP for events
SIP and presence
Instant messaging in SIP
- Stand-alone messages with MESSAGE
- Session based messaging with MSRP
B2BUA (Back to back User Agent)
- Requirements and Possibilities

Exercise 4 – Services

Presence
Instant messaging
Authorization and message encoding
Methods; SUBSCRIBE, NOTIFY, PUBLISH, MESSAGE

Classic Telephony Using SIP

Sending DTMF in VoIP
- DTMF and RTP, rfc2833
- DTMF and SIP
Merging PSTN Networks and SIP
- SIP for telephones SIP-T
- Q.1912.5 – SIP-I
Phonenumbers and SIP-addresses
- Tel: and SIP: URIs
- Address translation, interworking
- DNS and ENUM
Mobile SIP Telephony
- IMS, IP Multimedia Subsystem

Summary and Future

Summarizing the whole course
What to read first – List of RFC’s and Internet-Drafts
Links and references

Day 4-5

Troubleshooting Basics

Troubleshooting techniques
-        Generating baselines
-        Documenting the system
-        Reference Models
-        Isolating the error

Troubleshooting Tools

Overview of useful troubleshooting tools
-        Wireshark, Tcpdump
-        SipSAK, SIPp, SIP Scenario Generator
-        Ntop, MRTG,
-        DNS, dig and nslookup.

Practical Exercise 1

SIP Troubleshooting

Finding the rules
- IETF tools, IETF Workgroups
- The simple SIP Checklist

Important SIP Rules
-        Invite vs Non Invite
-        SDP Usage
-        Statehandling
-        Message Parsing
-        Registration and Caller preferences

Detailed Troubleshooting

Dialog Management

Rules for Dialog state management
-        Creating, modifying, releasing
-        Recording Routes and Route-set management
-        Early dialogs, early media, and PRACK.